This invention relates to water based dredges, and more particularly, to a grizzly for such a dredge which efficiently distributes recoverable material and waste to the appropriate locations after being deposited thereon.
Water based and floating dredges typically include at least one or more bucket or clamshell-type grabs which are lowered into a waterway to collect sand, clay, gravel, or the like from the bottom of the waterway. The grab typically deposits the collected material onto a grizzly which often includes a plurality of generally parallel bars forming a sieve. The dredged material often contains components whose value justifies recovering them such as sand and gravel. Other components such as clay are not desirable for recovery and are simply collected for removal and disposal. Separating the recoverable material from the unrecoverable, however, in the past has been a time consuming process. Previously, all dredged material was processed with a conventional grizzly through a material handling apparatus even when it contained nothing of value, such as clay or the like.
One prior method to determine whether dredge material includes recoverable matter is to inspect a load of dredge material in the grab when it breaks the water surface. If there is no recoverable material, the load is simply dumped into a refuse barge located nearby. If recoverable material is found in the grab, it is then deposited onto the grizzly for further processing. A problem associated with this system is the ability of the operator to accurately determine whether the dredged material includes recoverable material or simply clay while it is still in the grab. Visual inspection inside the grab is very difficult and an accurate determination of the contents therein is even more problematic. As a result, this process of dredging has proven to be very slow and time-consuming and does not offer a reliable determination of the components of the dredged material in the grab.
Another prior solution was to deposit the dredged material onto the grizzly for inspection by the operator. If the operator determined that the dredge material included worthwhile, recoverable material, it was processed through the material handling apparatus of the floating dredge. Alternatively, if the operator determined that the dredged material deposited on the grizzly consisted of clay and other undesirable materials, the bucket or clamshell grab is once again lowered to pick up the unrecoverable material from the grizzly and deposit it onto a waiting refuse barge.
This method enabled the operator to inspect the dredged material outside of the grab after it is deposited onto the grizzly. However, if the dredge material is clay and other waste, it must be picked up once again by the grab and transferred to the refuse barge for disposal. This process has also proven to be very time consuming and inefficient in the handling and determination of the components of dredged materials.